Method and composition for preserving sodium nitroprusside solutions

ABSTRACT

A method to extend a shelf life of a sodium nitroprusside solution includes: dissolving about two parts by weight of a 2-hydroxybenzyl alcohol and about one part by weight of a sodium nitroprusside in about seventy-five parts by weight of a polyethylene glycol. Compositions for preserving a sodium nitroprusside solution are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of co-pending U.S. provisional patent application Ser. No. 62/643,978, METHOD AND COMPOSITION FOR PRESERVING SODIUM NITROPRUSSIDE SOLUTIONS, filed Mar. 16, 2018, which application is incorporated herein by reference in its entirety.

FIELD OF THE APPLICATION

The application relates to sodium nitroprusside solutions and particularly to the shelf-life of sodium nitroprusside solutions.

BACKGROUND

Sodium nitroprusside solutions typically have a relatively limited shelf life of about 48 hours. As such, industrial distribution of a prepared solution for later use has not been practical.

SUMMARY

According to one aspect, a method to extend a shelf life of a sodium nitroprusside solution includes: dissolving about two parts by weight of a 2-hydroxybenzyl alcohol and about one part by weight of a sodium nitroprusside in about seventy-five parts by weight of a polyethylene glycol.

In one embodiment, the method includes: dissolving about 3 g of 2-hydroxybenzyl alcohol and about 1.5 g sodium nitroprusside in about 100 ml of polyethylene glycol at about 60° C.

In another embodiment, the polyethylene glycol includes a polyethylene glycol 300.

In yet another embodiment, the polyethylene glycol includes a PEG-300.

In yet another embodiment, the polyethylene glycol includes a PEG-400.

In yet another embodiment, the polyethylene glycol includes a PEG-1000.

According to another aspect, a composition for preserving a sodium nitroprusside solution includes: about two parts by weight of a 2-hydroxybenzyl alcohol and about one part by weight of a sodium nitroprusside dissolved in about seventy-five parts by weight of a polyethylene glycol.

In one embodiment, the composition includes: about 3 g of 2-hydroxybenzyl alcohol and about 1.5 g sodium nitroprusside dissolved in about 100 ml of polyethylene glycol at about 60° C.

In another embodiment, the sodium nitroprusside solution is a catalyst for an indophenol monochloramine reaction.

In yet another embodiment, the indophenol monochloramine reaction includes a water composition test or a water quality test.

According to yet another aspect, a composition for preserving a sodium nitroprusside solution includes: about two parts by weight of a 2-hydroxybenzyl alcohol and about one part by weight of a sodium nitroprusside dissolved in about seventy-five parts by weight of a component selected from the group consisting of a polyethylene glycol, an ethane-1,2-diol, a propane-1,2-diol, a polymer with a H—(O—CH2-CH2)n-OH structure either linear or cross linked, and a glycopolymer.

The foregoing and other aspects, features, and advantages of the application will become more apparent from the following description and from the claims.

DETAILED DESCRIPTION Definitions

Glycol like as used hereinbelow is defined to include diols and their polymers. Examples include, but are not limited to ethane-1,2-diol, propane-1,2-diol, polymers with the general structure H—(O—CH2-CH2)n-OH either linear or cross linked, and other glycopolymers.

Sodium nitroprusside solutions typically have a relatively limited shelf life of about 48 hours. As such, industrial distribution of a prepared solution for later use has not been practical.

Sodium nitroprusside solutions are useful as a catalyst for indicator solutions for water testing. For example, a sodium nitroprusside can be used as a catalyst for an indophenol monochloramine reaction in water composition and water quality testing processes. However, nitroprusside is an iron-based compound and the iron oxidizes and falls out, leading to an unacceptably short shelf-life.

What is needed is a method and composition for preserving sodium nitroprusside solutions, for example, to maintain the effectiveness of the indophenol monochloramine reaction.

Also, more generally, there is a need for a method and composition to preserve sodium nitroprusside solutions, so that prepared solutions can be distributed and stored with a much longer shelf life for later use.

It has been realized that dissolving sodium nitroprusside in polyethylene glycol, the solution can be preserved for an indefinite length of time, the shelf life having been shown to be at least greater than two years. For example, polyethylene glycol-300 (PEG-300) appears to be capable of preserving this solution indefinitely.

To my best understanding, the polyethylene glycol (e.g. PEG-300) works by preventing the oxidation of the Sodium nitroprusside by scavenging free radicals. Free radicals can be generated by contaminants or by UV light. The polyethylene glycol also sequesters any iron that may have oxidized to Fe3+. The polyethylene glycol also blocks UV light to reduce the formation of radicals.

Example 1: PEG-300 as an Antioxidant

Example 2: PEG-300 as a Sequestrant

PEG-300, and similar variants, is merely representative of a polyethylene glycol which can be used. Polyethylene glycol is available in many variants, such as, for example, PEG-300, PEG-400, PEG-1000, etc. Any suitable polyethylene glycol can be used. Moreover, it is believed that other “glycol like” chemicals can be used.

Example 3: The example is an indicator solution used in water testing. An exemplary indicator solution was prepared by dissolving about 3 g of 2-hydroxybenzyl alcohol and about 1.5 g sodium nitroprusside in about 100 ml of polyethylene glycol 300 at about 60° C.

Example 4: In an exemplary application, a sodium nitroprusside solution, such as the solution of example 1, can be used as a catalyst in an indophenol monochloramine reaction. The reaction cannot occur without the catalyst. Such indophenol monochloramine reactions are of particular interest for use in testing water.

Generally, a method to extend a shelf life of a sodium nitroprusside solution includes: dissolving about two parts by weight of a 2-hydroxybenzyl alcohol and about one part by weight of a sodium nitroprusside in about seventy-five parts by weight of a glycol (typically a polyethylene glycol) or glycol “like” material, such as, for example, ethane-1,2-diol, propane-1,2-diol, polymers with the general structure H—(O—CH2-CH2)n-OH either linear or cross linked, and other glycopolymers, or any other suitable polyethylene glycol.

In some embodiments, the polyethylene glycol liquid or a glycol like liquid material can be used at about 100% liquid polyethylene glycol or 100% liquid glycol like material without thinning. Thinning can be performed by mixing with another liquid, such as, for example, typically thinning by water. However, polyethylene glycol or glycol like material solutions thinned to between about 30% and about 100%, can be used as well. Successful tests were performed with about 30% and about 60% liquid polyethylene glycol thinned by water.

Any suitable temperature for dissolving can be used. Those skilled in the art will appreciate that in most embodiments, dissolving temperatures below about 70° C. will be used, because, for example, PEG-300 scorches and decomposes at about 70° C. In some embodiments a temperature of about 60° C. has been used.

Also, a composition for preserving a sodium nitroprusside solution includes: about two parts by weight of a 2-hydroxybenzyl alcohol and about one part by weight of a sodium nitroprusside dissolved in about seventy-five parts by weight of a glycol “like” material including solutions of any suitable glycol like material (e.g. any suitable polyethylene glycol).

Generally, a solution synthesized as described herein can be stored in a plastic or glass enclosure, typically a bottle. Shielding from light, including tinted glass or plastic is preferable. Also, storage is preferred at temperatures between about −15° C. and 65° C.

In summary, after dissolving sodium nitroprusside in polyethylene glycol, the solution can be preserved for an indefinite length of time, the shelf life having been shown to be at least greater than two years. For example, polyethylene glycol-300 (PEG-300) appears to be capable of preserving this solution indefinitely.

It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. 

What is claimed is:
 1. A method to extend a shelf life of a sodium nitroprusside solution comprising: dissolving about two parts by weight of a 2-hydroxybenzyl alcohol and about one part by weight of a sodium nitroprusside in about seventy-five parts by weight of a polyethylene glycol.
 2. The method of claim 1, comprising: dissolving about 3 g of 2-hydroxybenzyl alcohol and about 1.5 g sodium nitroprusside in about 100 ml of polyethylene glycol at about 60° C.
 3. The method of claim 1, wherein said polyethylene glycol comprises a polyethylene glycol
 300. 4. The method of claim 1, wherein said polyethylene glycol comprises a PEG-300.
 5. The method of claim 1, wherein said polyethylene glycol comprises a PEG-400.
 6. The method of claim 1, wherein said polyethylene glycol comprises a PEG-1000.
 7. A composition for preserving a sodium nitroprusside solution comprising: about two parts by weight of a 2-hydroxybenzyl alcohol and about one part by weight of a sodium nitroprusside dissolved in about seventy-five parts by weight of a polyethylene glycol.
 8. The composition of claim 7, comprising: about 3 g of 2-hydroxybenzyl alcohol and about 1.5 g sodium nitroprusside dissolved in about 100 ml of polyethylene glycol at about 60° C.
 9. The composition of claim 7, wherein said sodium nitroprusside solution is a catalyst for an indophenol monochloramine reaction.
 10. The composition of claim 9, wherein said indophenol monochloramine reaction comprises a water composition test or a water quality test.
 11. A composition for preserving a sodium nitroprusside solution comprising: about two parts by weight of a 2-hydroxybenzyl alcohol and about one part by weight of a sodium nitroprusside dissolved in about seventy-five parts by weight of a component selected from the group consisting of a polyethylene glycol, an ethane-1,2-diol, a propane-1,2-diol, a polymer with a H—(O—CH2-CH2)n-OH structure either linear or cross linked, and a glycopolymer. 